1. Field of the Invention
The present invention generally relates to admission control methods and admission control systems, and more particularly to an admission control method and an admission control system which carry out a session admission control based on a bandwidth measurement.
2. Description of the Related Art
As conventional session admission control methods, there are the bandwidth summation type admission control method and the bandwidth measurement type admission control method.
The bandwidth summation type admission control method summates the bandwidth which will be used and is declared when starting each session, and judges whether or not to accept the session depending on whether or not the summation of the bandwidth exceeds a preset bandwidth threshold value.
The bandwidth measurement type admission control method judges whether or not to accept the session depending on whether or not a sum of the bandwidth measured by a measuring apparatus exceeds a bandwidth threshold value.
The applicant is aware of Japanese Laid-Open Patent Applications No. 2005-236495 and No. 2006-020110.
The Japanese Laid-Open Patent Application No. 2005-236495 proposes a system which includes a bandwidth prediction means and predicts a data communication bandwidth at a time other than a measuring time, from start information and end information related to the data communication. The start or rejection of the data communication is determined based on the predicted bandwidth and the amount of bandwidth used by the network.
On the other hand, the Japanese Laid-Open Patent Application No. 2006-020110 proposes a method in which, between a user terminal and a service providing server, a transmitting end continuously transmits probe packets via the network, a receiving end utilizes a delay characteristic of the probe packets that are continuously received to compute an end-to-end usable bandwidth in a network path between the user terminal and the service providing server, and an admission control server receives a service request from the user terminal and judges whether or not to accept the service request by comparing the computation result of the end-to-end usable bandwidth and the bandwidth required by the requested service.
The bandwidth summation type admission control method manages the bandwidth which will be used and is declared when starting each session. Although the bandwidth can be closely controlled, managing the bandwidth which will be used and are declared by all sessions makes the bandwidth summation type admission control unsuitable for application to a large-scaled network and lack scalability. In addition, there is a problem in that it is difficult to know the actual bandwidth which will be used by each of the individual sessions.
There is also a method which requires a peak value (declared peak bandwidth) of each session to be declared, and summates the peak declaration bandwidth. However, even if the sum of the peak declaration bandwidth is actually not used, the admission for a new session will be rejected when the sum of the declared peak bandwidth exceeds the preset threshold value, and there is a problem in that the utilization efficiency of the network deteriorates.
The bandwidth measurement type admission control method manages only the sum of the bandwidth, and has a good scalability. However, if the traffic is concentrated during notification intervals of the bandwidth information to the admission control server, it is impossible to cope with an overshoot of the sum of the bandwidth exceeding the preset bandwidth threshold value or the bandwidth exceeding the physical bandwidth due the traffic concentration, and there is a problem in that the communication quality deteriorates.